Self-propelled wheelchair

ABSTRACT

A pair of nonsteerable main wheels are disposed at opposite sides of the frame of the wheelchair. A drive unit is disposed at the rear of the frame and is swingably interconnected therewith. This drive unit includes a drive motor and a pair of driving wheels. A self-braking driving transmission connects the motor with the driving wheels. A steering motor is also incorporated in the unit and a self-braking transmission connects the steering motor with a member fixed to the frame to cause swinging movement of the unit with respect to the frame.

[ 6] References Cited UNITED STATES PATENTS 1,233,846 7/1917Cochran..... 180/65UX 2,305,578 12/1942 Ulinski 180/791 2,482,203 9/1949Peterson et al. 180/65 2,978,053 4/1961 Schmidt 180/65X 3,280,93110/1966 Cahill et 180/23 Primary Examiner-A. Harry Levy Attorney-FredPhilpitt ABSTRACT: A pair of nonsteerable main wheels are disposed atopposite sides of the frame of the wheelchair. A drive unit is disposedat the rear of the frame and is swingably interconnected therewith. Thisdrive unit includes a drive motor and a of driving wheels. Aself-braking driving transmission cts the motor with the driving wheels.

Per Edward Carl Udden General Delivery, Timra, Sweden [21] Appl. No.824,907

May 15,1969

[] Patented Mar. 2, 1971 Apr. 9, 1965 Sweden 4698/ Continuation-impartof application Ser. No. 751,016, June 7, 1968, now abandoned which is acontinuation of application Ser. No. 540,652, Apr. 6, 1966, nowabandoned 8 Claims, 5 Drawing Figs. [52] US.

United States Patent [72] Inventor [22] Filed [32] Priority [54]SELF-PROPELLED WHEELCHAIR pair conne A steering motor is alsoincorporated in the unit and a self-braking transmission connects thesteering motor with a member fixed to the frame to cause swingingmovement of the unit with respect to the frame.

7 180/26, 180/42, ISO/79.1

Int.

B60k 17/30 [50] Field 180/52, 42,

26, 65, 60, 15 (MWC), 791

PATENTED MR 2 [EH SHEET 1 OF 5 SELF-PROPELLED WHEELCHAIR CROSS-REFERENCETO RELATED APPLICATION The present application is a continuation-in-partof a streamlined continuation application Ser. No. 751,016 filed on Jun.7, 1968 by Per E. C. Udden for Motor-Powered Wheelchair, which in turnwas a continuation of parent application Ser. No. 540,652, filed Apr. 6,1966 by Per E.C. Udden for Motor-Powered Wheelchair, the latter twocases having since become abandoned.

BACKGROUND OFTHE INVENTION Wheelchairs must enable a patient to movearound indoors in a safe and flexible manner. A principal requirement isthat the dimensions of the wheelchair must be kept within as narrowlimits as possible, and the steerable wheels should be arranged so thatthe radius of turnnof the chair is as small as, possible. As a result ofthese requirements, the classic design of a wheelchair has evolvedcharacterized by large main wheels located at opposite sides of thewheelchair and one or two smaller wheels disposed either in front of orbe-hind the main wheels and comprising link rollers with verticalpivots.

This type of wheelchair is not practical for use in outdoorapplicationsunless the supporting ground surface is quite smooth and hard.

Motor-powered or self-propelled wheelchairs have been developed forindoor use or for use onhard ground where there are obstacles such ascurbs or the like. Prior art wheelchairs have been provided with anelectrical motor and with large front wheels on each side of thewheelchair along with rear steerable wheels controlled by the electricmotor and positioned a certain distance behind the seat of thewheelchair in order to provide space for the motor and to enable thedriving function to be carried out. This latter type of wheelchair isexcessively large compared with a wheelchair of conventional design andaccordingly is impractical for use indoors. Additionally, suchwheelchairs have a tendency to turn over too easily when taking sharpturns or when turning at high speeds. Other types of wheelchairs havebeen designed for outdoor use including an electric motor and beingcapable of climbing over relatively difficult obstacles orslopes.However, such vehicles are not suitable for indoor use on flat surfacesor in hospitals or the like.

SUMMARY OF THE INVENTION associated supporting surface. This drive shaftis in turn connected by a self-braking transmission with the drivingwheels of the driving unit so that the driving wheels will be held. inposition when driving current to the electric driving motor isinterrupted.

The swingable unit includes a steering motor which is interconnectedthrough a self-braking transmission with a member fixed to. the frame ofthe wheelchair so that the unit can be swung with respect to thewheelchair. The unit will a.ccordingly remain in a fixed relationshipwithnrespect to the wheelchair when current is. interrupted to thesteering motor. The unit is swingable about an axis extendingsubstantially perpendicular to an associated supporting surface.

DESCRIPTION OF THE DRAWINGS.

FIG. 1 is a top rear perspective view illustrating a wheelchairaccording to the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingswherein like reference characters designate corresponding parts throughout the several views, the wheelchair of the present invention as seenin FIGS. 1 and. 2 includes. a frame 1 of steel tubing provided with acushion 2 and a backrest 3. The source of electrical energy for drivingthe wheelchair comprises electrical batteries 4 located below the seatand disposed between the two relatively large front wheels 5 which arenot steerable. This portion of the frame also supports armrests 6 andfootrests 7 as well as a control box 8 comprising means for electricallycontrolling the chair. Control box 8 is swingable around a substantiallyvertical axis 9 mounted on one of the armrests6. In this manner, thecontrol box can be swung away thus enabling the patient to drive thewheelchair very close to a table or the like.

A generally L-shaped frame portion-l0 is disposed at each side ofthe'chair:. The upper horizontal part of each L-shaped, frame portion ismounted for swinging movement about a pivot 11 located: adjacent thebackrest 3. In this manner, the frame portion 10 andaccordinglytheassociated armrest 6 and the footrest 7 can be swung outwardly asseen in FIG. 2 to. make it easier for the patient to move onto or off ofthe seat of the wheelchair,

A wheel 12 is provided for operating screw means whereby the footrest 7can be raised or lowered. by altering the angle between the horizontalpart of frame 10 and the downwardly extending part which carries thefootrest 7.

A driving unit includes an electric traction motor 13 the drive shaft ofwhich extends substantially parallel with the associated supportingsurface and which transmits torque to the rear wheels 14 of the driveunit. These rear wheels are supported by a fork, 15. A steering motor 17isarranged to swing the driving unit through the intermediary of aself-braking steering transmission indicated generally by referencenumeral 16 around a substantially vertical shaft 19. The steering motor17 isdrivingly interconnected with a steering transmission through abelt 18. Shaft 19 is fixed to a casing 20 enclosing various electricalcontrol equipment such as relays, etc., necessary for the driving andsteering of the chair. This casing 20 is rigidly connected to thebackrest of the chair in any suitable manner and the entire driving unitswings with respect to the frame 1, the casing 20 and the shaft 19 ashereinafter more fully described.

Referring now to FIG. 3. of the drawings, the current to the steeringmotor 17 is preferably supplied through a resetting servodevicecomprising two potentiometers. A master potentiometer 22 and a slavepotentiometer 23 are provided and are arranged in, a bridge circuit. Theposition of the slave contact 26 of the potentiometer 23 corresponds tothe position of the swingable unit with respect to the frame. The masterpotentiometer 22 is preferably mounted on one of the armrests 6 ofthe'chair and displacing of its contact 27 by means of a knob 21 resultsin a potential difference across the bridge which is fed to the steeringmotor through the intermediary of amplifiers 24 and 25. A displacementof the master potentiometer thus results in a potential differenceacross the bridge circuit which will cause the steering motorto turn theswingable unit in a direction so as to eliminate the potentialdifference across the bridge.

If this potential difference is less than a predetermined value, one oftwo 6-volt circuits will be completed across the steering motordepending on the polarity of the potential dif- 5 ference.

if, however, the potential difference is greater than said predeterminedvalue, one of two l2-volt circuits will be completed across the steeringmotor thereby changing the position of the slave contact 26 on thepotentiometer 23 which results in elimination of the potentialdifference. At a certain value of this difference, the l2-volt circuitacross the steering motor is interrupted and the 6-volt circuit isactivated. The steering motor will therefore continue in the samedirection but at a lower speed until the potential difference iseliminated.

To cause the steering of the wheelchair to be accurate, the resistancewinding of the slave potentiometer is preferably made with a higherresistance per degree of turning movement in its central portion than inits end portions against which the contact 26 rests when the swingableunit is turned in either direction. The master potentiometer on theother hand is of a construction so that a lower resistance per degree ofturning movement is provided in a central portion than in the endportions thereof. When the contact 27 engages the central portion of themaster potentiometer, this position corresponds to the relationshipwherein the swingable unit is positioned for straight forward movementof the wheelchair.

Referring now to FIGS. 4 and of the drawings, the selfbraking drivingtransmission and steering transmission are more fully described. Theelectric traction motor 13 includes the driving shaft 30 which issuitably journaled within the surrounding casing portion 31 and which isdrivingly connected with a worm screw 32. This worm screw 32 meshes witha worm wheel 34 which in turn is drivingly connected through adifferential indicated generally by reference numeral 36 in FIG. 5 whichthe two output shafts 38 and 40 to which the driving wheels areoperatively connected.

The belt 18 previously described as being operatively connected with thesteering motor 17 is also operatively connected with a pulley 50 fixedto the outer end of a shaft 52 suitably journaled in casing 60. Thisshaft is drivingly connected with a worm screw 54 which meshes with aworm wheel 56 as seen in i6. 4. This worrn wheel 56 is fixed to thevertical shaft 19 previously described which is in turn fixed to casing20 and the frame of the wheelchair. The upper portion 60 of the casingof the driving unit is connected to the lower portion 31 previouslydescribed and is rotatably journaled on shaft 19 by means of suitablebearing 62.

The driving transmission as well as the steering transmission comprisesworm gearing having a high transmission ratio which is for example 1:25or greater. This insures that a selfbraking action is obtained. The termself-braking accordingly means a transmission wherein the componentswill be held in fixed relationship when no power is applied to thetransmission. Accordingly, in effect, the transmission serves as a brakesince the components are held against movement when not power driven. Itis apparent that actuation of the steering motor will cause the entiredriving unit to swing about fixed shaft 19 so as to obtain the desiredsteering of the wheelchair,

As this invention may be embodiment in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, and since thescope of the invention is defined by the appended claims, all changesthat fall within the metes and bounds of the claims or that form theirfunctional as well as conjointly cooperative equivalents are thereforeintended to be embraced by those claims.

I claim:

1. A self-propelled wheelchair comprising a frame, a pair ofnonsteerable main wheels supporting said frame and disposed at oppositesides thereof, a drive unit swingably interconnected with said frame,said drive unit including a drive motor and a pair of driving wheels,said main wheels comprising the front wheels of the wheelchair, saiddriving wheels comprising the back wheels of the wheelchair, drivingtransmission drivingly connecting said drive motor and said drivingwheels, said driving transmission being self-braking when said drivingmotor is not operating, said drive unit also including a steerin motor,a steering transmission operatively connecting sai steering motor andsaid unit for swinging said unit and said drive motor and said steeringmotor relative to said frame, said steering transmission beingself-braking when said steering motor is not operating, said drive motorincluding a drive shaft extending substantially parallel with anassociated supporting surface, said drive unit being swingable about anaxis extending substantially perpendicularly to said associatedsupporting surface.

2. Apparatus as defined in claim 1 wherein said driving transmissionincludes worm gearing and a differential.

3. Apparatus as defined in claim 1 wherein said steering transmissionincludes a worm wheel fixed with respect to said frame, and a worm screwengaging said worm wheel, said worm screw being operatively connectedwith said steering motor.

4. Apparatus as defined in claim 1 wherein said driving transmissionincludes a worm screw drivingly connected with said driving motor, aworm wheel engageable with said worm screw, said worm wheel beingdrivingly connected with said driving wheels, said steering transmissionincluding a worm wheel fixed with respect to said frame, a worm screwengageable with said last-mentioned worm wheel, said last-mentioned wormscrew being operatively connected with said steering motor.

5. Apparatus as defined in claim 1 including a source of electricalcurrent for said steering motor, means connecting said source of currentwith said steering motor and including a resetting servodevicecomprising two potentiometer including a master potentiometer and aslave potentiometer arranged in a bridge circuit, said slavepotentiometer having a slave contact the position of which correspondsto the relative position between said drive unit and the frame, saidmaster potentiometer having a contact for producing a potentialdifference across the bridge which will cause the resetting servodeviceto turn the swingable drive unit in a direction so as to eliminate saidpotential difference.

6. Apparatus as defined in claim 2 wherein said slave potentiometer hasa higher resistance per degree of turning movement in its centralportion than its end portions.

7. Apparatus as defined in claim 2 wherein said master potentiometer hasa lower resistance per degree of turning movement in its central portionthan in its end portions.

8. Apparatus as defined in claim 2 wherein a small electrical currentthrough said bridge circuit results in a low-speed operation of thesteering motor, and a large current through the bridge circuit resultsin high-speed operation of the steeringmotor.

1. A self-propelled wheelchair comprising a frame, a pair ofnonsteerable main wheels supporting said frame and disposed at oppositesides thereof, a drive unit swingably interconnected with said frame,said drive unit including a drive motor and a pair of driving wheels,said main wheels comprising the front wheels of the wheelchair, saiddriving wheels comprising the back wheels of the wheelchair, drivingtransmission drivingly connecting said drive motor and said drivingwheels, said driving transmission being self-braking when said drivingmotor is not operating, said drive unit also including a steering motor,a steering transmission operatively connecting said steering motor andsaid unit for swinging said unit and said drive motor and said steeringmotor relative to said frame, said steering transmission beingself-braking when said steering motor is not operating, said drive motorincluding a drive shaft extending substantially parallel with anassociated supporting surface, said drive unit being swingable about anaxis extending substantially perpendicularly to said associatedsupporting surface.
 2. Apparatus as defined in claim 1 wherein saiddriving transmission includes worm gearing and a differential. 3.Apparatus as defined in claim 1 wherein said steering transmissionincludes a worm wheel fixed with respect to said frame, and a worm screwengaging said worm wheel, said worm screw being operatively connectedwith said steering motor.
 4. Apparatus as defined in claim 1 whereinsaid driving transmission includes a worm screw drivingly connected withsaid driving motor, a worm wheel engageable with said worm screw, saidworm wheel being drivingly connected with said driving wheels, saidsteering transmission including a worm wheel fixed with respect to saidframe, a worm screw engageable with said last-mentioned worm wheel, saidlast-mentioned worm screw being operatively connected with said steeringmotor.
 5. Apparatus as defined in claim 1 including a source ofelectrical current for said steering motor, means connecting said sourceof current with said steering motor and including a resettingservodevice comprising two potentiometer including a masterpotentiometer and a slave potentiometer arranged in a bridge circuit,said slave potentiometer having a slave contact the position of whichcorresponds to the relative position between said drive unit and theframe, said master potentiometer having a contact for producing apotential difference across the bridge which will cause the resettingservodevice to turn the swingable drive unit in a direction so as toeliminate said potential difference.
 6. Apparatus as defined in claim 2wherein said slave potentiometer has a higher resistance per degree ofturning movement in its central portion than its end portions. 7.Apparatus as defined in claim 2 wherein said master potentiometer has alower resistance per degree of turning movement in its central portionthan in its end portions.
 8. Apparatus as defined in claim 2 wherein asmall electrical cUrrent through said bridge circuit results in alow-speed operation of the steering motor, and a large current throughthe bridge circuit results in high-speed operation of the steeringmotor.